The effect of hypertension, induced by constriction of the renal artery, on the acceleration of lesions induced in dogs fed a diet already proven to be atherogenic and to induce increased rates of collagen synthesis in the lesion areas of atherosclerotic arteries will be investigated. The effect of hypertension on the expected regression of lesions in dogs returned to a "normal", non-atherogenic diet will also be studied. Activities of protocollagen proline hydroxylase (PPH), the enzyme which is responsible for synthesizing hydroxyproline from peptide bound proline, will also be determined in canine arterial tissue to find out whether increases in aortic collagen synthesis, as determined by incorporation of labelled proline into hydroxyproline in vitro, correlate with increases in PPH activity which is thought to be the rate limiting step in collagen synthesis. Spontaneously hypertensive rats and renal clipped rats will be utilized to determine the effect of hypertension on rates of biosynthesis of collagen in aortic tissue of normolipemic rats. Bibliographic references: Metabolic Interactions Among Polyunsaturated Fatty Acids in Response to an Atherogenic Diet. R. Balachandran and L. Ehrhart, Proc. Soc. Exp. Biol. Med., 149, 29-35 (1975). Non-arteriosclerotic Lesions in the Kidneys of Dogs Fed an Atherogenic Diet. K. G. McCullagh and L. A. Ehrhart, Exp. Mol. Pathol., 22, 400-416 (1975).